How Old is Too Old?

I'm in a weird place in my life where I'm in college and I'm in my twenties and I'm technically an adult but with my high student loans and low income I have no means to support myself. So my parents pay my bills, I live with my parents when school is out of session and they drive me around. While typing this and reading it out loud I realized how pathetic it sounded, but it must be relatively normal at my age because many of my friends live this way as well. But when does it stop being normal and start being down right inappropriate?

At what point are you crossing the line? Is it at 30 when you're a divorcee with a child and your living in a room in your parents house? Or is it when your in your late 40s and working on your billionth marriage with a few kids and your asking your elderly parents for money to buy a second car? When do you start paying your own bills and taking responsibility for yourself? Is there a timeline? Is their one of those clocks that you hold upside down and the sand drips one by one and once the sand runs out your on your own?

I'm actually not making fun of these situations, I'm just wondering because if there's any possible way I could live like this forever, I'd like to know about it.

-B.S.